Pop-under and pop-up traffic sources are types of advertising methods where a new window opens on a user's browser. The difference lies in how the window appears. Pop-up windows appear on top of the current browser window, while pop-under windows open behind the current window, so users don't see them until they close or minimize their current window. Both methods can be effective for driving traffic, but they work differently and may appeal to different audiences. Some people might find pop-ups annoying and close them immediately, while others might not even notice pop-unders until later. How do you think these methods impact user experience and conversion rates?